One of the dangers of excavation is that the bucket, tooth or blade of an excavator will encounter a buried object such as a subterranean pipe, electric line, telephone line or other structure and damage it before the operator of the excavating machine realizes that he is in the presence of such a buried object.
Accordingly it is known to bury alongside such objects, generally above them, a signaling material which is intended to be seen by the operator of the excavating machine before the latter encounters the protected buried object.
The material in the past generally has comprised a continuous rectilinear strip whose resistance to elongation (tensile strength) and rupture resistance are different from those of a carrying grid, e.g. of synthetic resin material.
As the shovel or bucket of the excavator slices through this material, the material may be visible in the bucket or in the excavating trench in which the material has been exposed by the excavation.
In practice, however, the band or strip is not always visible either in the contents of the bucket or shovel or in the trench which is formed.
Indeed, there is a tendency for the bucket to cut rather cleanly through this prior art signaling material so that neither the portion of the band contained in the shovel nor the portion of the band remaining in the ground and from which the former portion has been severed may be visible to the operator.
This is especially the case where the ground in which the excavation is made is rather loose so that the walls of the trench cave in at least to some degree to obscure the residue of the material which remains buried to either side of the trench.
Consequently, the continuous longitudinal strips of the signal materials hitherto used may obscure the signal during excavation of the presence of pipes disposed below the material when mechanized excavation is carried out in the manner described.